1. Field of the Invention
The present invention is broadly concerned with anti-reflective coatings which comprise low molecular weight core molecules in lieu of polymeric resin binders. In one embodiment, the small core molecules comprise epoxies with chromophores bound thereto.
2. Background of the Prior Art
Integrated circuit manufacturers are consistently seeking to maximize wafer sizes and minimize device feature dimensions in order to improve yield, reduce unit case, and increase on-chip computing power. Device feature sizes on silicon chips are now submicron in size with the advent of advanced deep ultraviolet (DUV) microlithographic processes. However, reducing the substrate reflectivity to less than 1% during photoresist exposure is critical for maintaining dimension control of such submicron features. Therefore, light absorbing organic polymers known as anti-reflective coatings are applied beneath photoresist layers in order to reduce the reflectivity normally encountered from the semiconductor substrates during the photoresist DUV exposure.
Prior art anti-reflective coating layers contain a polymeric resin with a light-absorbing chromophore either attached to, or blended with, the resin. Although high optical densities enable these polymers to provide effective reflectivity control, they also have numerous drawbacks. For example, these polymers have high molecular weights which cause problems during polymer blending. More particularly, the use of these polymers inhibits customization of the anti-reflective coating to the photoresist being utilized in the particular photolithographic process. Customization is extremely important because it allows for straighter profiles and better adhesion of the photoresist to the anti-reflective coating, thus resulting in better performance.
There is a need for new anti-reflective coatings which minimize or avoid the problems associated with prior art polymeric anti-reflective coatings.